As atomics moves ahead, such radiotherapy as Cobalt-60, linear accelerators and electron beams has been one of major means to cancer therapy. However, conventional photon or electron therapy has been undergone physical restrictions of radioactive rays; for example, many normal tissues on a beam path will be damaged as tumor cells are destroyed. On the other hand, sensitivity of tumor cells to the radioactive rays differs greatly, so in most cases, conventional radiotherapy falls short of treatment effectiveness on radioresistant malignant tumors (such as glioblastoma multiforme and melanoma).
For the purpose of reducing radiation damage to the normal tissue surrounding a tumor site, target therapy in chemotherapy has been employed in the radiotherapy. While for high-radioresistant tumor cells, radiation sources with high RBE (relative biological effectiveness) including such as proton, heavy particle and neutron capture therapy have also developed. Among them, the neutron capture therapy combines the target therapy with the RBE, such as the boron neutron capture therapy (BNCT). By virtue of specific grouping of boronated pharmaceuticals in the tumor cells and precise neutron beam regulation, BNCT is provided as a better cancer therapy choice than conventional radiotherapy.
BNCT takes advantage that the boron (10B)-containing pharmaceuticals have high neutron capture cross section and produces 4He and 7Li heavy charged particles through 10B(n,α)7Li neutron capture and nuclear fission reaction. As illustrated in FIGS. 1 and 2, a schematic drawing of BNCT and a nuclear reaction formula of 10B (n, α) 7Li neutron capture are shown, the two charged particles, with average energy at about 2.33 MeV, are of linear energy transfer (LET) and short-range characteristics. LET and range of the alpha particle are 150 keV/micrometer and 8 micrometers respectively while those of the heavy charged particle 7Li are 175 keV/micrometer and 5 micrometers respectively, and the total range of the two particles approximately amounts to a cell size. Therefore, radiation damage to living organisms may be restricted at the cells' level. When the boronated pharmaceuticals are gathered in the tumor cells selectively, only the tumor cells will be destroyed locally with a proper neutron source on the premise of having no major normal tissue damage.
In the existing neutron capture treatment planning system, the geometric angle of irradiation is determined and defined artificially based on experience. Due to the structure of the human body is quite complex and the sensitivity of various tissues or organs to radiation is also different. Therefore, a better angle of irradiation is likely to be ignored by relying on human judgment only, resulting in poor therapeutic effect. In order to achieve the optimization of the therapeutic effect, the irradiation angle of the beam is an essential part to be considered.
Therefore, it is necessary to propose a method for evaluating the irradiation angle of a beam.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.